Immunoglobulins, or antibodies, are a group of glycoproteins present in serum and tissue fluids of all mammals. There are five isotypes of Igs which all have a similar basic structure. The basic structure is a unit consisting of two identical light polypeptide chains and two indentical heavy polypeptide chains linked together by disulfide bonds. IgG is the major immunoglobulin in normal human serum accounting for 70–75% of the total immunoglobulin pool. The IgG class is the major antibody of secondary immune responses and the exclusive antitoxin class. Antibodies contribute to the protection against bacterial infections by agglutination and stimulation of phagocytosis.
Bovine colostrum, which can be defined as milk from the first three milkings or milk collected during the first 24 hours after parturition, is rich in nutrients, antibodies and growth factors. According to another, more common definition colostrum is obtained during the first three days after calving. It contains three classes of immunoglobulins, IgG, commonly divided into two subclasses IgG1 and IgG2, IgA and IgM. The main natural function of the colostrum immunoglobulins is to provide the newborn calf with passive immunity. The quality of colostrum is referred to its concentration of immunoglobulins; a good quality colostrum has >60 mg immunoglobulins/ml corresponding to >30 mg IgG1/ml.
Dietary exposure to bovine IgG can have several effects on the human immune system. As any foreign protein bovine IgG may represent a potent antigen and stimulate production of antibodies. Both bovine IgG subclasses bind to human monocytes, but only bovine IgG1 bind to human B cells. This binding to human mononuclear cells may influence the human mucosal and systemic immune responses. IgG1 of bovine origine has been shown to protect against infection by various enteric pathogens in animal and in humans.
There are many commercial products based on colostrum on the market, most of which are used as in the form of powder or tablets, beverages or food as nutritional food supplements or immune stimulants for health-oriented consumers and sports enthusiasts. Bovine colostrum supplementation in addition increases serum concentrations of growth factors and enables athletes to train harder, longer and more frequently.